1. Field of the Invention
The invention relates to a telecommunication system comprising a service switching point, a telecommunication terminal unit coupled to the service switching point by a first number of bus lines, and means for phantom power supply of the telecommunication terminal unit by the first number of bus lines.
2. Description of the Related Art
In such a telecommunication system, which particularly represents an ISDN-PBX (Private Branch eXchange), there is often the need to provide, in addition to the telecommunication terminal units which are generally enhanced-feature terminal units having many performance features, for example, added-feature telephones, a possibility of exchanging information signals within the telecommunication system, which possibility is simpler compared to the use of such telecommunication terminal units. This is the case, for example, where an emergency call system for emergencies for people in need of care is necessary. In emergencies, the operation of a complex telecommunication terminal unit such as, for example, an added-feature telephone, is too unreliable. Prior-art emergency call systems do not allow communication with a telecommunication system comprising a service switching point, so that an independent installation of the systems is necessary. The technical capacity of such a telecommunication system then remains unused. In addition, the separate cabling for the telecommunication system and the emergency call system is costly.